10 Family Cucurbitaceae Origin and History years (Zeven and Zhukovsky, 1975). The ancient Egyptians also cultivated cucumbers. Cucumis The cucurbits are largely tropical in origin with sativus var. hardwickii, a wild taxon native to different genera originating in Africa, tropical India, has been proposed as the wild progenitor of America, and Southeast Asia. Commercial cucur- the domesticated forms of C. sativus. Cucumbers bits are primarily herbaceous annuals that produce spread to China and Greece from India about distinctive tendril-bearing vines and are commonly 2,000 years ago (Whitaker and Davis, 1962; grown in temperate regions with long growing sea- Robinson and Decker-Walters, 1997). The Sikkim sons. Some are adapted to humid conditions while cucumber has been grown in the Himalayas as others are found in arid regions. Most are frost- food for centuries. intolerant although some species are more tolerant The cucumber also spread to Italy, and was a of low temperature than others. significant crop during the Roman Empire. In classical Rome, Pliny reported greenhouse pro- Taxonomy duction of cucumbers by the 1st century, and the Emperor Tiberius was said to have eaten them The Cucurbitaceae family is well defined but taxo- throughout the year (Sauer, 1993). Cucumbers nomically isolated from other plant families. The were probably spread to the rest of Europe by the family Cucurbitaceae consists of about 120 genera Romans. The earliest records of cucumber culti- and more than 800 species. Two subfamilies, vation appear in France by the 9th century, Great Zanonioideae and Cucurbitoideae, are well charac- Britain by the 14th century and the Caribbean at terized: the former by small, striate pollen grains and the end of the 15th century. Colonists introduced the latter by styles united into a single column. The the cucumber to North America by the mid-16th food plants all fall within the subfamily Cucurbi- century (Hedrick, 1919). Interaction between toideae and belong to two tribes: the Cucurbiteae Europeans and Native Americans spread cucum- and Sicyoideae. (Maynard and Maynard, 2000). bers throughout North America. Less than a cen- The genera Cucurbita , Cyclanthera and Sechium are tury later, European explorers observed a wide of New World origin. All other genera originated range of Native American peoples cultivating from the African or Asian tropics. In this chapter, the cucumbers along the east coast of North America production of cucumber ( Cucumis sativus ), netted from Montreal to Florida. Slaves also introduced and non-netted melons ( Cucumis melo ), watermelon cucumber directly to the Americas from Africa in (Citrullus lanatus ), and squash and pumpkin the early 1600s. By the 17th century, Native (Cucurbita spp.) will be discussed. Whitaker and Americans living in the Great Plains region were Davis (1962), Robinson and Decker-Walters (1997) also cultivating cucumbers (Wolf, 1982). and Rubatzky and Yamaguchi (1997) provide infor- mation about other crops in the family Cucurbitaceae. Botany CUCUMBER Cucumber (C. sativus) has a chromosome number Origin and History of n = 7, West Indian Gherkin ( C. anguira ), n = 12, and Armenian cucumber (C. melo), n = 12. Commercial The center of origin of cucumber is believed to be cucumber cultivars are warm-season, frost-sensi- India where it has been grown for thousands of tive annuals that are cross-pollinated by bees. 10 © Gregory E. Welbaum 2014. Vegetable Production and Practices (G.E. Welbaum) Welbaum_Ch10.indd 10 8/4/2014 4:07:33 PM Plants commonly have a trailing or climbing Fruits can be spherical, blocky, oblong or elong- growth habit, although some bush cultivars with ated in shape and variable in size. Fruit surfaces shortened internodes also exist. Root systems are vary in the number and size of spiny warts, which extensive but shallow. Stems are square with stiff are usually more apparent on young fruit. bristle hairs, unbranched tendrils and generally Cucumber fruit are consumed immature when their range in length from 0.4 to 3 m (1.3 to 9.8 ft). flavor is mild and seeds are small and underdevel- Tendrils at each node help anchor plants and allow oped. Cucumbers are used for different purposes climbing on supports. Cucumber petioles are 3–15 cm depending on their characteristics (Fig. 10.1). (1.2–5.9 in) long. Rough leaf blades have a tri- Cultivars are often divided into the general cat- angular ovate shape from 5 to 25 cm (2.0 to 9.8 in) egories of “fresh market” or “processing” to describe wide with three- to five-angled regions or shallow- their intended uses. Cultivars grown for fresh lobed sinuses and a pointed apex (Rubatzky and market usually have a fruit length-to-width ratio of Yamaguchi, 1997). at least 4:1, dark-green color when immature, thick Cucumber plants exhibit monoecious (separate skin, slightly tapered stem and blossom ends. The male and female flowers on a plant), andromo- seed cavity of fresh market types is usually larger noecious (separate perfect and male flowers on than processing cultivars. the same plant) or gynoecious (all female) sex Cultivars developed for processing often have expression. Sex expression is genetically con- smaller vines, fruit with a length-to-width ratio of trolled but modified by the environment and about 2.5:1, bicolored pale and darker green chemicals. Application of auxin or ethephon immature color, thin skins, blocky shape and more favors both earlier and a higher percentage of prominent warts. The warts bear white or black female flowers, while gibberellin delays female loosely attached spines (spicules) in their centers. flower formation and percentages. Auxin and Fruit with white spines turn from green to white or ethephon favor female flower development while yellow at full physiological maturity when seeds gibberellin stimulates the formation of male have fully developed. The color of black-spined flowers. In monoecious cultivars, staminate flowers fruit changes from green to orange at maturity. appear first and are several times more abundant Black-spined fruit have thinner skin and lighter than pistillate flowers. Flowers occur at the fruit color compared to white-spined fruit and for nodes, staminate in clusters or singly with only many years were preferred for processing because one flower in a cluster opening at a time. Pistillate they have a more attractive appearance after pick- flowers are borne singly on the main stem and ling. However, black-spined cucumbers tend to lateral branches in monoecious types and singly prematurely develop their mature orange color at or in clusters on the main stem and lateral the stem and blossoms ends under environmental branches on gynoecious types. The large inferior stress or when over mature, so more white-spined ovary of pistillate flowers resembles a miniature cultivars have been developed for processing in fruit. Both staminate and pistillate flowers are recent years. 1–3 cm (0.4–1.2 in) in diameter with a yellow, showy five-lobed corolla. Flowers are open for a West India gherkin single day and if not adequately pollinated rap- idly abort. Small-fruited cultivars of pickling cucumbers are Flowering is influenced by photoperiod with sometimes sold as gherkins. However, the West regard to the number and sex of the flowers India or true gherkin (Cucumis anguria) belongs to formed. During short days, there is a tendency for a different species and has a different appearance earlier and more frequent pistillate flowering. Low and characteristics than C. sativus. West India temperatures may cause a similar response. gherkin is an annual, monoecious climbing vine Conversely, high temperature and long days pro- with flowers, leaves, tendrils and fruit smaller than mote male flower formation (Rubatzky and cucumber. Fruits, which are spiny, yellow, oval and Yamaguchi, 1997). High nitrogen promotes vegeta- about 5 cm (2 in) long, are eaten fresh, cooked or tive growth and inhibits flower formation. pickled. The plant may self-seed, escape from culti- Environmental stress (water, nutrient, etc.) pro- vation, and become an aggressive weed (Whitaker motes female flower formation. and Davis, 1962). Cucurbitaceae 11 Welbaum_Ch10.indd 11 8/4/2014 4:07:34 PM Types of cucumbers Bush or vining Parthenocarpic or pollinated Processing Fresh market Mechanical harvest or hand pick Hand harvest (Preserved in vinegar) (sometimes used for fresh market) Slicing 6L or 8 to 1W (Dark) Pickling 3L:1W (Light) Greenhouse Outdoor Black spine White spine (Orange at maturity) (White at maturity) Tender skin Regular 1. Beit Alpha 2. Burpless (Asian) 3. American Slicing Fig. 10.1. Cucumber cultivars come in many different shapes and sizes that were developed for specific uses and markets. This figure summarizes some of the major commercial types. Types and Cultivars dill seed) to make pickles and other products (Fig. 10.2). There are many diverse cultivars of cucumber grown Pickling cultivars have special characteristics throughout the world. Cultivars differ in their degree that make them suitable for processing in vinegar of bitterness caused by cucurbitacins that accumulate (Motes, 1975). Resistance to carpel separation and in tissues of plants in the family Cucurbitaceae. The bloating allow pickling cucumbers to retain their function of cucurbitacins is believed to be defense shape and integrity during the brining process. against herbivores. Cucurbitacins are chemically clas- Fruit are harvested for processing while immature sified as steroids but often occur as glycosides (Chen and not more than 12.5 cm (5 in) long. Cucumbers et al ., 2005). Non-bitterness in fruit is inherited as a for processing may be open-pollinated or F-1 hybrids simple recessive trait. Since plant breeders have been and are either hand or mechanically harvested, selecting against bitter flavor for many years, fruits of maturing 55–60 days from seeding. To ensure a most modern cultivars are free of bitterness. Some concentrated set for mechanical harvesting, gynoe- older heirloom cultivars may develop bitter taste, par- cious cultivars are often preferred.